As alloys exhibiting shape memory effect, there are known nonferrous-metal alloys including Ni--Ti alloys and Cu alloys as well as ferrous metal alloys such as Fe--Pd alloys, Fe--Ni alloys and Fe--Mn alloys. Among others, Fe--Mn alloys are inexpensive, and thus, because of their commercial value, various alloys of this Fe--Mn series are reported in patent literatures, for example, Fe--(15.9-30.0%) Mn alloys in JP A 55-73846, Fe--Mn--(Si, Ni, Cr) alloys in JP A 55-76043, Fe--(20-40%)Mn--(3.5-8%)Si alloys in JP A 61-76647 and Fe--(15-30%)Mn--N alloys in JP A 63-216946. furthermore, JP A 62-112720 discloses a method for enhancing shape memory effect of a Fe--Mn--Si alloy wherein a so-called training effect by repeating a cycle of working at a rate of up to 20% and heating to a temperature of at least 400.degree. C. is utilized.
However, ferrous metal shape memory alloys are generally disadvantageous in low corrosion resistance. JP A 61-201761 discloses examples of Fe--Mn--Si alloys whose corrosion resistance is improved by adding Cr. However, the Cr content taught is too low, i.e. not more than 10.0%, to achieve corrosion resistance well comparable with that of stainless steels. Furthermore, JP A 63-216946 teaches to improve corrosion resistance of ferrous metal shape memory alloys by adding Cr. Again, however, the Cr content disclosed is 10% or less and it is not taught how to realize a desired level of shape memory characteristics with the ferrous metal shape memory alloys having Cr, which is a ferrite former, in excess of 10% incorporated therein.
On the other hand, as to general stainless steels, "Scripta Metallurgica, 1977, vol. 5, pp.663.about.667" reports that SUS304 steel exhibits shape memory effect, if it is deformed at -196.degree. C. and then heated to room temperature, however, its shape recovery is too small to put it to practical use.